This study examines how coliphage T3 is inactivated by bacterial receptors. Klemperer found that phage resistance to inactivation varies across individual particles and follows a log-normal distribution. When plotting phage survival against log receptor concentration, a sigmoid curve emerges that becomes linear when data are converted to probits. This linear relationship indicates normally distributed resistance. The researcher developed a practical assay method using probits to measure receptor activity in bacterial extracts from Escherichia coli B and Salmonella typhi. The method proved sensitive enough to detect differences in receptor reactivity between bacterial species and could quantify receptor activity even after treatments like antiserum exposure or storage. Unlike previous findings with phage 1, the log-log plot of survival versus time was non-linear for T3, but the probit analysis revealed both phages share underlying heterogeneity in their particle resistance properties.

Key findings

• Coliphage T3 particles show variable resistance to inactivation following a log-normal distribution rather than uniform resistance.
• A probit analysis method provides a linear relationship between phage survival and log receptor concentration, enabling accurate assay of receptor activity in bacterial extracts.
• Receptors from different bacterial hosts (E. coli B vs. S. typhi O901R) show different reactivities with coliphage T3, evidenced by different slope values in probit plots.
• The assay method is sufficiently sensitive to detect partial inactivation of receptors caused by antiserum treatment or storage degradation.
• The heterogeneity in phage particle resistance may be a general property of bacteriophages, explaining apparent differences between various phage-receptor systems.